The methods and systems described below provide for optimal treatment of fibroadenomas. A fibroadenoma is a benign tumor found in women's breasts. They are small, solid, round, rubbery masses that are typically found in breast self-exams or mammography. Fibroadenomas are harmless, but may be painful, palpable and emotionally bothersome, and the may mask other lesions that would otherwise be visible to mammography. Fibroadenomas are removed to alleviate pain and to alleviate the emotional burden of living with a breast lump. Even when the breast lump is confirmed to be a benign fibroadenoma, many women elect removal for these reasons. Typically, fibroadenomas are removed by lumpectomy, which is an open surgical procedure. Open surgical recision requires a fairly large incision, creates an unsightly scar on the breast and a scar inside the breast that interferes with mammography, and it requires general anesthesia.
In our prior patent, Littrup, Method and System for Cryoablating Fibroadenomas, U.S. Pat. No. 6,789,545 (Sep. 14, 2004), and Van Bladel, et al., Device For Biopsy And Treatment Of Breast Tumors, U.S. Pat. No. 6,494,844 (Dec. 17, 2002), we disclosed systems for treating fibroadenomas in the breast of female patients. In U.S. Pat. No. 6,789,545, we proposed a cryosurgical treatment regimen comprising a period of high power freezing to very low temperature, followed by a period of low power freezing, followed by a period of thawing, and a repetition of high power freezing and low power freezing, followed by thawing and/or warming of the cryoprobe. In this procedure, the cryoprobe was operated to achieve a cryogenic temperature of −150° C. during the high-power freezing period, as measured by a temperature sensor within the cryoprobe. The cryoprobe was then operated to maintain a cyrogenic temperature of −45° C. or below. This procedure has proven to be quite effective and reliable. The U.S. Food and Drug Administration currently requires that this gold standard of treatment (double freeze-thaw to the critical temperature of −40° C. within the mass) be used in the treatment of fibroadenomas.
However, our experience with fibroadenoma patients has led to the development of the new procedure described below which is faster and more efficient, but which retains the advantages of our prior method including creation of a smaller iceball fitted to the fibroadenoma, reduced ablation of healthy tissue surrounding the fibroadenoma, reduced potential for damage to the skin overlying the fibroadenoma, and reduced resorption time for the ablated mass. In our experience, we have determined that fibroadenoma regrowth is insubstantial, regardless of thaw achieved during the thaw cycle. Thus it appears that the “thaw-induced” cell death mechanism must be substantially complete upon warming of the ice ball to 0° C. (or even earlier), so that complete thawing is unnecessary. Whether the iceball thaws completely or not at all does not affect the long-term success of fibroadenoma cryoablation. Also, the cooling-induced cell death mechanism appears to be complete, for fibroadenomas and perhaps other lesions, by the time the tissue has reached −20° C. Further cooling to lower temperatures, and cooling for extended periods beyond that necessary to reach this temperature, do not appear to affect the long-term success of fibroadenoma cryoablation. Thus, though there is no reasonable expectation, based on the state of art, that the methods and systems described below would provide adequate treatment, our experience indicates that, for fibroadenoma, treatments which represent a departure from the current gold standard of cryoablation are safe and effective.